This invention relates to an output control method and apparatus and to a control system for creating data output to a peripheral device such as a printer, and then outputting the data to the peripheral device.
In a printing system having a host computer and a printer connected to the host computer via an interface (e.g. a Centronics interface), the printer analyzes print information that enters from the host computer and creates bitmap data as output data output to a printer engine. The printer modulates a laser beam, for example, on the basis of the bitmap data thus created and scans the laser beam across a photosensitive drum to expose the drum and record an image.
In a case where the host computer has a printer emulation function, the printer is so adapted that it can process a plurality of print control languages. In accordance with an application program run by the user, printing processing can be executed while the printer is switched between the emulation mode and an ordinary mode. In this case, the printer is provided with a switch for changing over the printer control language and with a card slot used to instruct the changeover.
In a case where the image processing means in this conventional printer is fixed, the image data output to the printer are transmitted upon being converted to a format suited to the fixed processing means. Further, in a case where the printer has a plurality of image processing means, the image data are changed to data having a data format conforming to one of these image processing means before being transferred from the host computer.
Consequently, the following problems are encountered with the conventional printing system described above:
(1) Since the data sent to the printer have a single data format, the original image data, even if it is highly efficient in terms of content, cannot be transmitted to the printer as is.
(2) Since the data sent to the printer have a single data format, the data are sent to the printer as is even when the data are inefficient in terms of content (i.e. even when the data has a high degree of redundancy).
(3) Since the format of the data sent to the printer is fixed, the format of the data transferred cannot be changed in conformity with the content of the image data output to the printer.
(4) Since the data necessary to select the format of the data sent to the printer are fixed, control conforming to the functions possessed by the printer cannot be carried out.
Accordingly, an object of the present invention is to provide an output control method and apparatus as well as an output system in which, when image data sent to an output unit or output device are highly efficient, the image data are sent to the output unit or output device as is, whereas image data that are inefficient are sent upon first being converted.
Another object of the present invention is to provide an output control method and apparatus as well as an output system in which transferred content can be constructed in conformity with the content of image data and selection of a data format can be performed automatically.
A further object of the present invention is to provide an output control method and apparatus as well as an output system in which data necessary for selecting data format are obtained from an output unit or output device, whereby control in conformity with the output unit or output device can be carried out.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.